'Sunshine' vitamin D crucial say scientists

9th March 2010

Danish researchers have discovered that vitmin D is vital in activating human defences and could help the fight against infectious diseases and global epidemics, and could also be useful in the search for new vaccines.

The researchers found that immune systems' killer cells, known as T cells, rely on vitamin D to become active and remain dormant and unaware of the possibility of threat from an infection or pathogen if vitamin D is lacking in the blood.

Carsten Geisler of Copenhagen University's department of international health, immunology and microbiology, who led the study said: "When a T cell is exposed to a foreign pathogen, it extends a signaling device or 'antenna' known as a vitamin D receptor, with which it searches for vitamin D.

"This means the T cell must have vitamin D or activation of the cell will cease. If the T cells cannot find enough vitamin D in the blood, they won't even begin to mobilise."

Scientists have known for a long time that vitamin D is important for calcium absorption, and that there is a link between levels of the vitamin and diseases such as cancer and multiple sclerosis.

"What we didn't realise is how crucial vitamin D is for actually activating the immune system - which we know now," Geisler wrote in the study in the journal Nature Immunology.

Even though there is no definitive studies on the daily vitamin D dose, experts recommend 25 to 50 micrograms, said Geisler.